Anxiety disorders are estimated to affect approximately 13.3% of 18-54 year-old adults in a given year (NIMH Publication #01-4584). This high prevalence rate makes treatment and prevention of anxiety disorders pivotally important. These goals can only be met with an understanding of the neural basis of anxiety, both to direct treatment and prevention approaches and to assess their effectiveness. This AREA grant proposal describes the use of an animal model of anxiety to examine the behavioral, neural and hormonal changes associated with exposure to predator odor with and without prior exposure to a stressor. Previous work has demonstrated that serotonin mediates the effects of uncontrollable tailshock on exaggerated freezing behavior, which can be considered a form of anxiety. The present studies are designed to expand that research to examine how naturalistic stressors impact defensive responding. It is hoped that a focus on ethologically relevant responses in rats will better correspond to the development of anxious behavior in humans. The primary goat of the proposed studies is to examine the impact of a naturalistic stressor, exposure to the elevated plus-maze, on predator odor responses. The specific aims of this research are to 1) examine the specificity of predator odor responses as a defensive behavior, 2) to map the corresponding neural changes in areas known to be influenced by odor and stress, and 3) to characterize the hormonal response to predator odor. This research will be conducted at Connecticut College, a selective liberal arts college which has established faculty/student research collaboration as a priority. Future studies will build on the goals of the present research by exploring how anxious behavior can be prevented.